Lens.



Patented Apr. 2, I90l.

C. GRAF.

LENS.

(Applicltion filed Jan. 4, 1901.)

(No Model.)

avweulioz mtg HOW/ Q4101 new:

UNITED STATES PATENT OFFICE.

OHRISTOPH GRAF, OF CLOSTER, NEWV JERSEY.

$PEGIFIUATION forming part of Letters Patent No. 671,066, dated April 2,1901. Application filed January 1, 1901. Serial No. 42,041. (No model.)

To all whom it may concern.-

Be it known that I, Cnnlsrorn GRAE, a citizen ofthe United States,and aresident of Closter, in the county of Bergen and State of New Jersey,have invented certain new and useful Improvements in Lenses, of whichthe following is a specification, reference being had to the drawingsforming a part hereof.

This invention relates to lenses for optical purposes; and it has forits object the prod uction of an achromatic aplauatic lens with aperfect astigmatic correction and a larger relative aperture than lensesheretofore made.

In the drawings, Figure 1 is a sectional view of one form of my compoundlens. Fig. 2 is a sectional view of two lenses such as shown in Fig. 1combined as a double objective. Fig. 3 is a sectional view of anotherform of my compound lens. Fig. 4 is a sectional view of two lenses suchas shown in Fig. 3 combined as a double objective.

Similar characters indicate similar parts throughout the views.

My compound objective is composed of four lenses, two positive and twonegative, the two negatives beingjuxtaposed andlying between the twopositives. Each of the lenses is of a different refracting power, thetwo outer positive lenses having one the highest and the other thelowest refracting power of the set. The two negative lenses aretherefore of intermediate refracting power and are so disposed in thecombination that the negative lens of the less refracting power isadjacent to the positive lens of the highest refracting power, while thenegative lens of the greater refracting power is adjacent to thepositive lens of the least refracting power. The lenses are cementedeach to its neighbor or neighbors.

In the form shown in Fig. 1, P, the first positive, is a double-convexor collecting lens of crown-glass,with a refractive index of about 1.61.N, the first negative, is a double-concave dispersing-lens offlint-glass, with a refractive index of about 1.53. N the secondnegative, is a diverging meniscus lens of flintglass, with a refractiveindex of about 1.57. P, the second positive, is a convergingconcavo-convex or collecting meniscus of crownglass, with a refractiveindex of about 1.51. As seen in the drawings, the lenses N N are incontact, located between the lenses P P the lens P being in contact withthe lens N and the lens P being in contact with the lens N In asymmetrical double combination, with the outer vertices separated, asshown in Fig. 2, the diaphragm D is placed midway between the twolenses. A lens so made may be worked with an aperture of about F 5.5.For a single lens the diaphragm D may be placed before the lens P asshown in Fig. 1.

In the modification shown in Fig. 3, P the first positive, is adouble-convex or collecting lens of crown glass, with a refractive indexof about 1.61, as in the lens shown in Fig. 1. N the first negative, isa concavoconvex dispersing-lens of flint-glass, with a refractive indexof about 1.53. N, the second negative, is a double-concavedispersing-lens of flint-glass, with a refractive index of about 1.57.P, the second positive, is a converging concavo convex or collectingmeniscus of crown-glass, with a refractive index of about 1.51, as inFig. 1. The lenses N N are in contact, located between the lenses 1 P,the lens P being in contact with the lens N and the lens Pi being incontact with the lens N As with the lens of Fig. 1, the diaphragm D maybe located before thelens P. This modified lens may likewise be used ina symmetrical double combination, as shown in Fig. 4, the diaphragm Dbeing placed midway between the two lenses.

Having described my invention, what I claim as new, and desire to secureby Letters Patent, is-

1. A compound lens, consisting of four single lenses juxtaposited, eachof a different refracting power, the two inner lenses being negative,and of intermediate refracting power,and the two outer lensesbeingpositive, one of the highest refracting power, and the other of thelowest refracting power,substantially as described.

2. Acompound lens, consisting of four single lenses juxtaposited andcemented together, each of a different refracting power, the two innerlenses being negative and of different refracting powers, the outer lensadjacent to the negative lens of less refracting power being positiveand of the highest refracting power, and the outer lens adjacent to thenegative lens of greater refracting power being positive and of theleast refracting power, substantially as described.

3 A compound lens, consisting of four single lenses juxtaposited andcemented together, each of a different refracting power, the first lensbeing a double convex and of the highest retracting power, the secondlens, adjacent thereto, being a double concave of the third highestrefracting power, the third lens, adjacent to the second lens, being adiverging meniscus of the second highest refracting power, and thefourth lens, adjacent to the third lens, being a converging meniscus ofthe fourth or least refracting power, sub- 15' stantially as described.

In testimony whereof I have signed my name, in the presence of twosubscribing wit- .ne'sses, this 18th day of December, 1900.

OHRISTOPH GRAF.

Witnesses:

CHAS. P. SOHMID, Jr., THEODORE T. DORM'AN.

